1. Field of the Invention
The present invention relates in general to controls for elevators, and in particular to an elevator door restrictor for preventing elevator doors from being opened between floors.
2. Description of the Prior Art
A new national standard for elevator codes has recently been promulgated by the American Society of Mechanical Engineers, and has been widely adopted by many local building code authorities. It requires door restrictors for blocking the inner doors of elevators from being pushed open more than a total of four (4) inches when elevator cars are disposed between floors. The code provides a standard that the elevator must be within eighteen (18) inches of being perfectly aligned at a floor before the door restrictor allows the inner doors to be pushed open. Preferably the inner elevator doors may be pushed open a slight distance, not more than a total of four (4) inches, so that persons trapped within an elevator car between floors may look out into the elevator shaft, call for help and circulate fresh air.
Prior art elevator door restrictors have been provided by mechanical latches which prevent the inner doors of elevator cars from being pushed open when the elevator cars are between floors. The prior art mechanical latches have mechanical linkages which engage cams located at each floor to move the mechanical latches from a latched position to an unlatched position when the elevator passes by each floor. These prior art mechanical latches do not prevent the inner doors from being pushed open while elevator cars are moving past a floor. Additionally, the mechanical linkages are typically noisy, making noise as the elevator passes each floor.